Polymer particles in the form of powders are of great importance in a variety of areas including plastics, membrane coatings, films, drug manufacture, biomedical engineering and instrument manufacture. More particularly, polymer powders comprising spherical and monodisperse particles of a predetermined size can be used in fundamental studies of materials and physics, as well as in calibration of scientific instruments.
The keen interest in these spherical and monodisperse size-controlled polymer particles is exemplified by attempts to produce them aboard the space shuttle Columbia during two different missions. In these space shuttle experiments, large latex particles were grown by emulsion polymerization under gravity-free conditions. "MADE IN SPACE, SRM 1960: 10-MICROMETER POLSTYRENE SPHERES", Office of Standard Reference Materials, Room B-311, Chemistry Bldg., National Inst. of Standards & Technology, Gaithersburg, Md. 20899.
In the past, a number of methods have been used to produce polymers. For example, one method includes polymerization in bulk. This process is not well controlled. Furthermore, the product may not be homogeneous.
Another process is emulsion or suspension polymerization, where polymer particles are obtained by evaporating the suspension agent. This process is also not easy to control and is slow. Furthermore, the particles obtained are not pure as they contain surfactants.
In another prior process, particles are created by gaseous reactions and homogeneous nucleation. This process is complicated and very sensitive to adverse conditions, and may result in fine particles only.
It would be advantageous to produce spherical, and monodisperse polymer particles of a predetermined and controlled size, or polydisperse polymer particles quickly and inexpensively.